The present invention is directed to apparatus and methods for simultaneously pasteurizing a large number of in-shell eggs without substantially impairing their functionality. This invention further relates to a flat for use in the apparatus and methods.
It is desirable to pasteurize viable and non-viable in-shell eggs for a variety of reasons. The most important of these reasons is providing in-shell eggs that are safe for consumption by the public at large. Pasteurization can reduce the level of various microorganisms that are typically present both on the shell and inside the shell of a whole egg, including within the egg albumin and within the egg yolk.
With regard to pathogens present on and/or inside an in-shell egg, especially a chicken egg, a common pathogen is Salmonella. A variety of other microorganisms may also be present on and/or within in-shell chicken eggs. See E. M. Funk, Pasteurization of Shell Eggs, University of Missouri, College of Agriculture, Agricultural Experiment Station, Research Bulletin 364, pp. 1-28 (May 1943), incorporated herein by reference in its entirety.
While the following comments are directed to chicken eggs, these comments may also apply to other types of in-shell eggs. In the early 1900's, it was appreciated that chicken eggs were pathogenically contaminated on their outer shell. Such contamination was believed to be caused by surface contact with, for example, fecal matter, contaminated animal feed, other contaminated material and the like. It was further believed that in-shell eggs were contaminated within the egg shell by penetration of pathogens through the pores thereof. It has only recently been discovered that bacteria such as Salmonella and, especially, Salmonella enteritidis, enters the egg yolk of an in-shell egg via trans-ovarian transmission (i.e., from the mother to the egg even before the egg is laid by the hen). See, M. E. St. Louis et al., The Emergence of Grade A Eggs as a Major Source of Salmonella enteritidis Infections, JAMA, Volume 259, No. 14, pp. 2103-2107 (Apr. 8, 1988), incorporated herein by reference in its entirety. Until the presence of trans-ovarian transmission was discovered in the 1980's, the need to pasteurize against such trans-ovarian contamination remained unrecognized.
To provide in-shell chicken eggs safe for human consumption without cooking, the Food & Drug Administration (FDA) has proposed requiring at least about a 3 to 5 log reduction in the pathogen count of various microorganisms present in and/or on the in-shell eggs. Those skilled in the art of in-shell egg pasteurization will recognize that a 5 log reduction refers to a reduction in the count of a pathogen by a factor of 5 logs or to a value of 1/100,000 of the initial value. Unless about a 3 to 5 log reduction in, for example, the Salmonella count or that of other pathogens on and/or inside an in-shell chicken egg, particularly, in the egg yolk, is achieved, such an egg does not comply with the proposed requirements of the FDA relating to in-shell chicken eggs.
While a 3 to 5 log reduction may be generally provided by heating an in-shell egg, care must be taken not to substantially impair its functionality. The functionality of the in-shell egg affects its market value. For example, if the functionality of an in-shell egg is impaired, then the egg albumin will not rise or foam (as desired or necessary) upon whipping, or the yolk will not be firm and the like. A functionally impaired egg is considered an inferior egg for its culinary uses including baking and the like.
The functionality of a pasteurized in-shell egg may be measured by a number of methods. For example, one measure is the ability of the egg albumin to properly rise or foam upon whipping. A functionally impaired egg may manifest an inordinately reduced whipping volume, a substantially increased whipping time and/or the like. Another measure of functionality is the height of an egg yolk and/or albumin after the in-shell egg has been cracked open on a flat, substantially horizontal, ambient temperature (e.g., 20-25.degree. C.) surface. Typically, the functionality may be measured in Haugh units. See E. M. Funk, Stabilizing Quality in Shell Eggs, University of Missouri, College of Agriculture, Agricultural Experiment Station, Research Bulletin 362, pp. 1-38 (April 1943), incorporated herein by reference in its entirety.
An in-shell egg that exhibits a Haugh value of less than about 60 Haugh units would be considered to have a substantially impaired functionality. However, for example, if in a batch of 100 eggs, 90% of the eggs have a value of no less than about 60 Haugh units, then it is considered that the functionality of the batch has not been substantially impaired. Preferably, it is desirable to have 90-95%, more preferably 95-98% and most preferably 99-100% of pasteurized in-shell chicken eggs in a given batch to have a Haugh value of no less than about 60 Haugh units.
Ordinarily, in-shell eggs are collected from the hen house, washed, size graded and separated according to their grading (e.g., S, M, L, XL, Jumbo and the like). Thereafter, the eggs may be pasteurized to achieve at least about a 3 to 5 log reduction. To achieve the necessary pasteurization level, the eggs may be heated for a set time period for the particular size (i.e., grade) of in-shell eggs. Data relating to pasteurization times and temperature is known. Such information may be used to achieve at least about a 3 to 5-log reduction in the pathogen count. See co-pending Davidson International Application No. PCT/US96/13006 (U.S. application Ser. No. 08/519,184), entitled Pasteurized In-Shell Chicken Eggs And Method For Production Thereof, filed on Aug. 9, 1996, incorporated herein by reference in its entirety. See also, International Application No. PCT/US95/00254 (WO 95/18538), and U.S. Pat. No. 2,423,233, each incorporated herein by reference in its entirety. None of these patents, patent applications or publications disclose simultaneous pasteurization of a large number of in-shell eggs. Further, none of these references address the problems encountered when attempting to pasteurize large commercial quantities of in-shell eggs without impairing their functionality.
While pasteurizing may be accomplished by heating the eggs to the desired pasteurization level, several difficulties are encountered when attempting to pasteurize commercial quantities of in-shell eggs in an efficient, fast and cost-effective manner. Typically, large volume commercial operations involve transporting one or more batches of, for example, several hundred to thousands of dozens of eggs (e.g., 1,000 to 6,000 dozen eggs) at a time. However, such large commercial quantities of in-shell eggs cannot be pasteurized together as a single batch without substantially impairing egg functionality (e.g., at least about 60 Haugh units per batch) using known procedures.
When pasteurizing commercial quantities of in-shell eggs to a safe level, the ability to maintain their market quality is critically important. The market quality of pasteurized eggs should be sufficient to market them to the public (for consumption). However, maintaining market quality depends on successfully pasteurizing commercial quantities of in-shell eggs without substantially impairing their functionality. Thus, pasteurization as well as stabilization of egg quality (e.g., a Haugh value of no less than about 60 Haugh units, preferably no less than about 70 Haugh units and, more preferably no less than about 80 Haugh units) in a cost efficient manner is paramount, especially for large scale commercial operations to remain successful.
However, pasteurizing, for example, a thousand or more dozens of in-shell eggs at a time within about an hour or two has been exceedingly difficult or impossible to accomplish, if the functionality of substantially all of the in-shell eggs in a batch is not to be substantially impaired. This is especially so when attempting to achieve a pasteurization level of at least about 3 to 5 logs.
U.S. Pat. No. 2,423,233 discloses a conventional process for preserving eggs for consumption. This process, however, fails to address various problems associated with pasteurizing of commercial quantities of in-shell chicken eggs without substantially impairing their functionality. There is, therefore, a need to provide apparatus and methods for rapidly and cost effectively pasteurizing in-shell eggs without substantially impairing their functionality.